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[lly]

Dear friends,
What it exactly means "finishes=125; tir=0.005"; I saw on the drawings.
I am an non english reader.

Thanks

 

[moseley]

lly,
In my experience what this means is that the surface finish is called out to be 125rms with a +/- .005". There is a gauge to measure this which most of the machine shops do have. In short this means that they want a fairly smooth surface finish, I believe this is standard for many valve seats. Hope this helps.

 

[butelja]

125 probably means 125 µin RMS. (Microinches root mean square)

TIR is total indicated runout. It is measured by rotating the cylindrical member and measuring the runout using a dial indicator. It can be rotated either on precision centers or v-blocks. There are pluses and minuses to each approach.

 

[moseley]

butelja,
Thank you for that correction, I have dealt with this before, it has just been a while.